The present invention relates to implantable medical leads for connection between a stimulating control device and one or more stimulation or sensing electrodes and methods of manufacturing such leads, and more particularly to implantable leads and lead assemblies with coiled electrodes and means for implanting the same.
Systems and methods for electrical stimulation of electrically excitable tissue within the body of a living subject have been developed utilizing stimulating electrodes and a signal generator or control device to supply electrical charges in a controlled or predetermined manner. Such systems and methods have been developed specifically based upon a desired condition, such as to alleviate pain or to stimulate muscle movement, and based upon the application with a subject's body. For bodily applications where alleviation of pain is the goal, one or more stimulating and/or sensing electrodes can be implanted within nerve tissue, the brain or spinal cord for blocking pain sensation by electrical stimulation. For muscle tissue stimulation, a stimulating electrode can be implanted in a muscle tissue, whereby electrical current that is typically provided as pulses can cause muscle tissue reaction that may be controlled to cause movement of a subject's body part. Sensing electrodes are used for determining actions of the body.
Signal generators can determine when, how long, and/or the amperage of current pulses that are to be applied for the specific application, and often include hard-wired circuitry, a microprocessor with software and/or embedded logic as the controlling system for determining and dictating current pulses. Such signal generators may also be implanted within the subject's body, and typically such an implantation is done to position the signal generator close to the stimulating and/or sensing electrodes, with interconnecting medical leads for conducting current pulses to and from the stimulating and sensing electrodes. Implantable medical leads and externally utilized leads for these purposes are typically insulated conductors or conductive elements (e.g., a conductor disposed within a lead body), with conductive terminations at both ends for electrical connection with the signal generator and one or more electrodes. Implantable medical leads further have requirements for safe interbody use such as tissue compatibility, surgical procedure dynamics, and body fluid accommodation.
Signal generation and muscle tissue stimulation systems have more recently been envisioned for more complex control of a subject's bodily actions. One particularly complex muscular control concept has recently been considered for the purpose of re-teaching a subject how to swallow, the condition of inability to swallow being known as dysphagia. Techniques and methods of stimulating muscles within the neck region of a patient for the purposes of causing specifically determined muscles to react as a swallowing effect are described in PCT Publication No. WO 2004/028433, having a publication date of Apr. 8, 2004. Specifically, by implanting electrodes in two or more muscles of the upper airway musculature and connecting the electrodes with a signal generator that provides coordinated control signals, a swallowing action can be induced in the patient. Other specific techniques and methods are also disclosed in U.S. Pat. Nos. 5,725,564; 5,891,185; 5,987,359; 6,104,958; and 6,198,970; all to Freed et al. Other techniques and methods are disclosed in U.S. patent application Ser. No. 11/611,365, filed Dec. 15, 2006, and entitled “Method and Apparatus for Assisting Deglutition.” The teachings of each of these references are incorporated herein by reference in their entireties.
For these and a variety of other implanted electrode stimulation treatments, conventional leads may not be optimal. For example, it may be difficult at best to achieve long term fixation of a medical lead's electrode at or against certain target tissue sites when employing conventional electrode configurations. Some muscles/muscle tissues are one such example whereby suturing or otherwise affixing a flat or ring-type electrode to the muscle's surface may not maintain a long term connection. Similarly, other target tissue sites are sensitive/fragile, or may require a more intimate contact with the electrode(s) to achieve the desired application of electrical impulses thereto via the electrode(s). Even further, muscles (as well as some other targeted tissue) will repeatedly move (e.g., contract) over time; the electrode used under these circumstances preferably exhibits some extensibility to accommodate these movements. Unfortunately, conventional flat or ring-type electrodes may not be able to satisfy these constraints.
To better meet the above needs (as well as possibly other needs) presented by some surgical sites, a coiled electrode can be employed. Coiled electrodes are generally known, can provide a form of self-fixation to the target tissue, ensure intimate contact with the tissue in question, and can be naturally extensible. For certain applications, it is desirable that the selected coiled electrode be soft or pliable so as to exhibit desired flexibility and/or minimize possible tissue damage. Coiled electrodes formed of platinum and iridium are an example of an acceptable coiled electrode material construction. With these and other similar coiled electrodes, the implantation technique generally entails mounting the coiled electrode to the conductor of the medical lead, delivering the medical lead to the target site, and then inserting the coiled electrode into the target tissue. As part of this insertion, a pulling force is applied to the distal end of the coiled electrode in piercing or otherwise inserting the coiled electrode into the target tissue. Due to the soft nature of many coiled electrodes, this pulling force can cause the coiled electrode to overtly stretch in a relatively inelastic manner, thus possibly damaging the coiled electrode.
In light of the above, a need exists for a coiled electrode lead assembly configuration promotes insertion of the coiled electrode into targeted tissue without overtly stretching the coiled electrode.